1. Field of the Invention
The present invention relates to audio data processing, and, in particular, to methods and apparatuses for controlling the flow of audio data during teleconferencing.
2. Description of the Related Art
It is desirable to provide a system for teleconferencing between a plurality of terminals operating on a local area network (LAN), where each terminal comprises a computer, an audio capture device, and an audio playback device. In order to provide teleconferencing between the terminals, audio data from each terminal is transmitted in "packets" of data over the LAN to each of the other terminals.
If the flow of audio data over the LAN and if the capture and playback processing of the audio data by the terminals are not properly controlled, the quality of the audio playback at the receiving terminals will suffer. The flow of audio data to the terminals over a LAN must be carefully regulated, because:
Local area networks typically do not guarantee the delivery of packets of audio data in an exact period of time; PA1 The clocks of the computers on the LAN and the audio capture and playback devices controlled by those computers are typically not synchronized; and PA1 Some audio playback devices obtain their digital sound information by accessing a fixed memory buffer via direct memory access.
If, for example, a receiving terminal is overwhelmed with audio data, that is, if the flow of audio data to the terminal exceeds the capability of the terminal's audio playback device, then increased audio latency may occur. Audio latency refers to the delay between one teleconference participant's speech and the rendition of that speech on the terminals of the other teleconference participants. If the audio latency gets sufficiently large, the quality of the teleconference will become unacceptably low.
On the other hand, if a receiving terminal is intermittently starved of audio data, that is, if the flow of audio data to the terminal become too low, then rhythmic breakup may occur. Rhythmic breakup refers to the periods of silence that occur when the supply of audio data is insufficient for the buffering requirements of an audio playback device. Like large audio latency, rhythmic breakup also diminishes the quality of the teleconference.
What is needed is a system for teleconferencing between terminals on a LAN that reduces the problems of audio latency and rhythmic breakup associated with too much and too little data, respectively.
It is accordingly an object of this invention to overcome the disadvantages and drawbacks of the known art and to provide a system for teleconferencing between a plurality of terminals on a LAN.
It is a further object of this invention to provide a teleconferencing system that controls the flow of audio data over a LAN.
It is a further object of this invention to provide a teleconferencing system that controls the processing of audio data at the terminals.
It is a further object of this invention to provide a teleconferencing system that reduces problems of audio latency and rhythmic breakup associated with too much and too little data, respectively.
Further objects and advantages of this invention will become apparent from the detailed description of a preferred embodiment which follows.